#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll N = 2e5 + 10;
ll a[N];
#define yes cout<<"YES"<<endl
#define no cout << "NO" << endl
void solve()
{
    ll a, b, c;
    cin >> a >> b >> c;
    if(a==b&&b==c)
    {
        yes;
        return;
    }
    if(b==a+1||c==b+1)
    {
        yes;
        return;
    }
    no;
    return;
}
int main()
{
    ll t = 1;
    //cin >> t;
    while (t--)
    {
        solve();
    }
    return 0;
}